Advice on building roof for artificial grass

[frusc]

I've got a ~70/sqm town garden which is 6 ft below the first floor of my house. Having got planning permission to raise and deck the garden with some storage underneath part of it, I've been mulling over the options for a couple of years. Now with the planning nearing its 3 year expiry I have to get this job done.

I had originally thought of having a second roof under the decking for the storage area. But with a little one now on the seen the Mrs has been pushing for some grass. It appears artificial grass has come a long way and also I've seen applications on roof terraces. So I'm thinking perhaps this would be a good option for use on top of the storage area, with the rest decked.

The storage area will be 3mx6m (I can reduce the span to 1.5m with pillars in the middle since its just for storage) and I plan to slope the roof towards the longer 6m side where water will be collected and put into a soak away. It will purely be for storage not habitation. Has anyone done anything similar?

My concerns are:

1) Obviously first and foremost the roof needs to be strong enough for people to walk on.
2) The artificial grass is porous, so I'll need some sort of drainage layer between the roof and the grass. Also some sort of impact layer would be good since it will be laying on a solid surface. Not sure if I can get an underlay which does both.
3) While the roof will be sloped, I'd prefer if the grass above was level with the decking. So I'd need some sort of levelling layer as well.
4) The currently floor level to proposed decking level is just head height. So I'd need to excavate to accommodate the roof/grass/underlayers. Therefore ideally I'd like to keep this to a minimum (but doing the job right is the priority).

I will be using a contractor to do the work, but thought it best to be armed with some facts first (to make sure the contractors are suitable), hence this post. Any advice would be greatly appreciated.

Also any pointers to artificial grass/suitable undlerays and a good decking supplier (leaning towards using IPE) would be greatly appreciated.

Thanks

 

[tomfe]

You only have to start not finish for you planning permission not to lapse.

 

[frusc]

Thanks. A relative has told me the same. So worst case I plan to make a start and buy myself some more time.

But ideally I'd just like to get it done. Otherwise I'll have a persistent headache from the Mrs while the garden is left half ripped up :/

 

[^woody^]

There are significant structural and design implications with this type of roof, so you might ned someone to sort that out, rather than winging it

 

[frusc]

There are significant structural and design implications with this type of roof, so you might ned someone to sort that out, rather than winging it

You are pretty much echoing my own concerns which is why I posted here. I don't plan on doing a DIY job, I will be using a contractor.

I do know builders who've done work for me and family before. But I don't think any have done what is essentially a roof terrace, so pretty sure I'll be using someone new. Which is why I wanted to get an idea before I start canvassing contractors so I know who's telling me the right things and therefore suitable.

 

[^woody^]

Building regulations will also apply. The contractors who tell you that are the ones that might be appropriate to use.

 

[frusc]

I assume you mean building regs will apply for the terrace style roof if I go that route rather then sub structure as I'd originally planned?

Perhaps its simpler to stick to the sub structure. And just figure out how to accommodate the artificial grass in the decking above (ideally want grass and decking at same level).

 

[frusc]

Well i'm getting more and more confused which way to go.

Had one of the contractors I'm considering come in for an initial look before quoting. Advice was as follows:

Option 1) Proceed with "conventional" decking/artificial grass. Use steel beams and wooden joists for frame. This will provide open area underneath (less supports needed as the steel beams can span a greater distance) to build outbuilding. Building control/regs won't apply as I already have planning permission for decking structure (the actual raised platform) and the outbuilding below is not attached to this, is less then 30m2, non habitable, below 2.5m high, etc

Option 2) Build outbuilding with block and beam roof. Add screed layer/asphalt to make watertight. Lay Underlay and grass on top. Deck rest of the area using conventional frame. He will have to check if the fact the roof of the outbuilding now forms part of the raised platform means building regs/control would be required.

Any thoughts on this? Will have two more people look at it before making a decision. And also drop in to my local planning department for their thoughts (but first will start enough work to ensure I'm safe with regard to planning permission lapsing).

NB: I spoke to a couple of block and beam suppliers to ensure this was a suitable application for that product (as mostly it seems to be used for indoor/ground floor). They confirmed it can be used in this way (provided as always it was installed to their design/drawings/specs).